Two important elements of the frame of a vehicle are the front rails and the rockers. The front rails provide support for components such as the engine and are the main energy-absorbing deformable members. Because of the wheels, the front rails are set somewhat close to the centerline of the vehicle. The rockers support the mid-section of the frame and are placed farther from the centerline of the vehicle than the front rails to maximize the interior occupant space. The rockers are also placed lower than the rails from a side-view perspective.
One way of distributing load to the underbody of a vehicle is to use underbody rails. These have the disadvantage of adding height to the vehicle on which they are used, and they require substantial length. A well-known alternative practice is to connect the front and rear rails to the rocker with torque boxes. The torque box rigidly connects the rail and the rocker and provides the mechanism to transfer longitudinal deforming force from the rails to the rocker.
It has been general practice to form a torque box from sheet metal that is stamped and welded or otherwise joined together. But this usual construction of a torque box from sheet metal requires more than one piece, resulting in multiple forming tools and complicating the assembly process. And the need to tune a torque box to withstand the initial peak impact force while still distributing such a force to the rocker may be a cumbersome process. It may also be difficult to vary the thickness to tune the conventional torque box that is made of stamped sheet metal, because stampings are typically of constant gage. In addition, adding ribs or gussets would require additional parts.
It would be desirable to have a support structure that would overcome the above problems.